1. Field of the Invention
The present invention relates to an absorbent article such as a disposable diaper, a pad for the incontinence of urine or a sanitary napkin and, more particularly, it relates to an absorbent article including a surface structure having an excellent fittingness on a body.
2. Related Art
The absorbent article of the prior art such as the disposable diaper, the pad for the urinary incontinence or the sanitary napkin generally includes: a liquid-permeable top sheet disposed on the liquid-receiving, inner side; a liquid-impermeable back sheet disposed on the outer side; and an absorbent core made of pulp and a highly absorbent polymer (or super absorbent polymer: SAP) and sandwiched between the two sheets.
In such an absorbent article, a structure has been investigated for improving the fittingness on a urinary organ and thereabout, when applied to a crotch, to prevent excreted liquid such as urine or menstrual blood from leaking transversely. For example, there has been practiced a structure, in which a relatively bulky cushion layer made of a hydrophilic fiber layer is disposed on the liquid-receiving side of the absorbent core, or a structure in which an absorbent material layer smaller than the absorbent core is disposed on the liquid-receiving side of the absorbent and such a cushion layer as above is further disposed on the absorbent material layer. In another structure, gathers for preventing the transverse leakage are disposed on two side edges of the absorbent core.
However, the aforementioned absorbent article provided with the cushion layer cannot cover the individual differences in the shape of the crotch reliably at all times. Especially, the disposable diaper or the pad for the urinary incontinent for taking care of old people frequently fails to fit the crotch. This is because the old people are seriously different among the individuals in the width of the crotch, in the flesh of the crotch, abdomen or hip or in the flabbiness or wrinkles of the skin, as compared with infants. If the absorbent article fails to fit the crotch, the excreted liquid will easily leak along the skin to the outside of the absorbent article to wet the wears or bedclothes. This problem is more serious for the old people who excrete far more liquid for one piss than the infants. When such an absorbent article unfitted for the crotch is worn, moreover, irregular wrinkles are formed on the liquid-receiving side of the absorbent article to make it harder for the absorbent article to absorb the excreted liquid.
Against these problems, there exists an absorbent article which is curved to fit the crotch by providing transverse leakage preventing gathers on two side edges of an absorbent core so that the absorbent core may follow the gathers. However, even in this absorbent article, because the central portion of the absorbent core is less curved than the side edges thereof, the absorbent core is difficult to fit the whole crotch, thereby to leave gaps between the absorbent core and the crotch. As a result, a large amount of excreted liquid may move transversely through the gaps so that its leakage cannot be prevented by the transverse leakage preventing gathers.
The present invention is to solve the problems of the prior art thus far described and has an object to provide an absorbent article in which a surface structure disposed on the liquid-receiving side easily fits the crotch, the urinary organ or the inguinal region.
Another object of the invention is to provide an absorbent article which is so curved as to easily fit the crotch of the wearer thereby to prevent the transverse leakage of the excreted liquid.
According to an aspect of the invention, there is provided an absorbent article comprising: a surface structure having a liquid-permeable surface sheet located on a liquid-receiving side; a back sheet; and an absorbent core sandwiched between the surface structure and the back sheet, wherein, in an area including at least a centerline extending in a longitudinal direction of the absorbent article, the surface sheet is corrugated to form recesses and ridges extending in the longitudinal direction and alternating with each other in a transverse direction perpendicular to the longitudinal direction, and the ridges are given an elastically shrinking function in the longitudinal direction at least at their crests or vicinities thereof so that the surface structure is formed into a curved shape.
With the surface structure of the absorbent article of the invention, the surface sheet constructing the surface structure elastically shrinks in the longitudinal direction so that the surface structure is curved. As a result, the absorbent article is curved in its entirety so that the liquid-receiving side easily fits the crotch, the abdomen or the back (or hip). Therefore, the excreted liquid can be quickly absorbed by the absorbent article while being prevented from leaking transversly. To give the elastically shrinking function, preferably, elastic members extending in the longitudinal direction are attached to the crests of the ridges of the surface sheet.
Moreover, because the ridges thus formed have degrees of freedom against the vertical and horizontal pressures i.e., because they can be flexibly deformed, the ridges can fit the roughness of the urinary organ, the crotch or the inguinal region. In other words, the surface structure comes into contact with the wearer""s body to have a larger contact area for eliminating gaps between the absorbent article and the wearer""s body. As a result, the excreted liquid is prevented from flowing transversely in such gaps and its leakage is further reduced.
Preferably, the surface structure further includes a liquid-permeable support sheet located between the surface sheet and the absorbent core, and the support sheet is bonded to the surface sheet at an interval in the transverse direction to thereby form the recesses. In this case, more preferably, a cushion layer is provided inside of the ridges such that the cushion layer is sandwiched between the surface sheet and the support sheet.
Preferably, ridges in a center region including the longitudinally extending centerline are different in height from other ridges in two side regions outside of the center region.
Preferably, cover sheets are provided to cover longitudinal end portions of the ridges.